Automated shift transmissions have been used for quite some time in the different motor vehicles. For instance, devices are provided to support the force of the shift elements during gear changes, in particular, shift transmissions in commercial vehicles which are designed as multi-group transmissions. Multi-group transmissions comprise two or more transmission groups, most likely configured in series, where their combination can create a large number of gear steps. They comprise, for instance, a split transmission as the input transmission and a main transmission or intermediate transmission, and a range transmission thereafter following as an output or a reduction transmission. Such shift transmissions offer especially detailed gear steps with twelve or sixteen gears, for instance. Compared to manual shift transmissions, they are characterized by a high operating comfort and are, in comparison to automatic transmissions, especially economical with regard to the manufacturing and operating costs.
For the execution of shift operations, such shift transmissions at least partially use the supply pressure of the vehicle in which they are installed. The shift elements, meaning the main cut-off valves and their following shift valves, for instance, are either directly supplied with this supply pressure or system pressure, respectively, or with a lowered constant upgrading pressure, for instance, via pressure reduction valves. That means that the load of the shift elements, the shift timing, the noise of the shifting, etc., can not, or only to a small extent, be influenced.
However, already known through DE 2006 040 476 A1 is a hydraulic or pneumatic control device, for an automatic shift transmission, in which the pressure can be controlled in a gear shift mechanism space which is designed as a pressure storage, which is positioned in front prior to the main cut-off valve or the main cut-off valves, respectively. Hereby, prior to a shift operation, the changing pressure requirement is estimated or a pressure drop in the system is calculated by means of a pressure sensor and, depending on the pressure requirement, one, two or more parallel positioned main cut-off valves will be opened to meet this pressure requirement. However, when the pressure requirement is estimated, this method is not precise or control of the main cut-off valves happens too late because the control can only be executed, for instance, when the pressure sensor has detected and processed a pressure drop in the system. In particular, this known method does not allow a variable match of the supply pressure to the particular special requirements of a certain shift scenario.